Question: If $x \oslash y = x-4y$ and $x \bigtriangledown y = 3x-4y$, find $-5 \bigtriangledown (2 \oslash 1)$.
Explanation: First, find $2 \oslash 1$ $ 2 \oslash 1 = 2-(4)(1)$ $ \hphantom{2 \oslash 1} = -2$ Now, find $-5 \bigtriangledown -2$ $ -5 \bigtriangledown -2 = (3)(-5)-(4)(-2)$ $ \hphantom{-5 \bigtriangledown -2} = -7$.